The present invention relates to drives for electric and hybrid vehicles. In particular, the present invention relates to determining a rotary movement of an electrical machine. Further particularly, the present invention relates to a circuit for evaluating the resolver sensor signals in a vehicle, to a controller for a vehicle, having a circuit according to the invention, and also to a vehicle, in particular an automobile, having a circuit according to the invention and/or a controller according to the invention.
In electric and hybrid vehicles, a drive power for the vehicle is supplied, at least partially, by an electrical machine, and therefore to an electric motor. In order to actuate an electrical machine of this kind in a preferred manner, it is usually useful to determine accurate information about the current operating state of the electrical machine.
In order to determine said information in this way, a so-called resolver sensor on the electrical machine is usually used, said resolver sensor being used to detect the rotation speed and angular position of the rotor of an electrical machine.
Rotation speed and angular position are of central importance for motor control. An evaluation logic system is used in order to evaluate the raw data, which is supplied by the resolver sensor, in such a way that the required measurement variables of rotation speed and angular position are supplied to a controller, for example in the form of digital data values.
FIG. 1 shows a conventional resolver sensor with rotor excitation.
Winding 10a is fitted to the rotor 6 of an electrical machine. Said winding is excited by a sinusoidal AC voltage. Two windings 10b, 10c which are fitted to the stator with a perpendicular orientation in relation to one another receive a voltage which is induced by winding 10a. 
The amplitudes of the voltages which are induced in the windings 10b, 10c are determined in this case by the angle of the rotor or of the winding 10a and in this case correspond in each case to the sine and cosine of the angular position of the rotor.
However, resolver sensor and evaluation logic system are usually only simply present.
FIG. 2 shows a conventional evaluation arrangement of a resolver sensor 4.
In this case, controller 20 has microprocessor 12 which actuates a resolver actuation/evaluation circuit 14, a so-called resolver chip 14 or resolver digital converter circuit 14, by means of a reference signal 25. Said resolver actuation/evaluation circuit 14 is supplied, by way of example, with a voltage of 5 Vdc.
In this case, resolver chip 14 generates, by way of example, an excitation signal waveform, for example sinusoidal oscillation at 10 kHz and with ±2.5 VPeak. This sinusoidal oscillation is converted into an excitation signal waveform with ±10 VPeak by means of an amplifier element 18 and fed to the resolver sensor 4 in winding 10a. 
Therefore, region 26 represents the resolver actuation. Resolver sensor 4 is schematically illustrated in a manner fitted to the motor of an electrical machine 16.
The resolver sensor data 28 is in turn supplied by means of filter element 22, for example a low-pass filter, to the resolver chip 14 as sine or cosine signals with, for example, ±2.85 Vpeak.
The resolver chip 14 itself is connected to microprocessor 12 via data link 24a and supplies digital signal values relating to the rotation speed and angular position of the rotor of the electrical machine 16 to the microprocessor 12. Furthermore, fault information is made available to the microprocessor 12 via data link 24a. 
The evaluation logic system can contain simple diagnosis of the resolver sensor signals which identifies various types of fault in the resolver signals.
However, this fault information generally does not contain faults which occur within the resolver chip since these cannot be sufficiently well detected or the resolver chip does not have suitably internal provisions in order to be able to itself check that it is operating in a fault-free manner.
Therefore, faults within the evaluation logic system itself and in the transmission of data to a further-processing microprocessor of a controller usually cannot be identified. These faults include, for example, register faults, data bit faults, addressing faults of the evaluation logic system, frozen data, independent reconfiguration of the evaluation logic system, and defects in computation units, etc.
Undetectable faults of this kind can therefore result in faulty rotation speed and angle values being transmitted, but these nevertheless being considered to be valid by a downstream controller and possibly resulting in, therefore faulty, actuation of the motor. Such faulty control of the motor can therefore lead to this kind of faulty actuation of the electrical machine, and therefore said electrical machine executes a rotary movement which is not adequate for the situation or operates with an undesired torque. The risk of “undesired vehicle movement” or “undesired vehicle movement direction” can also be caused by failure of the resolver chip.
Faulty actuation of this kind can lead, for example, to undesired acceleration of the vehicle, to blocking of the drive axle, or even to destruction of the IGBTs which actuate the motor.